Powder reactor for self-propelled projectiles



APril 1961 c. A. SOMVILLE 2,978,867

POWDER REACTOR FOR SELF-PROPELLED PROJECTILES Filed Jan. 6, 1958 V NTOP di /925 A. JamnZZe POWDER REACTOR FOR SELF-PROPELLED PROJECTILES Charles A. Somville, SIa Chaussee dAnvers, Burcht-lez- Anvers, Belgium Filed Jan. 6, 1958,Ser. No. 107,295 Claims priority, application Belgium Mar. 29, 1957 5 Claims. c1. 6035.6)

This invention relates to powder reactors for rocket projectiles as to the Bazooka type and other automotive devices.

Projectiles of this category are designed, generally, to carry a certain payload for which it is logical to provide as large a part as possible of the projectiles allowable overall weight. Therefore the other components of the projectile, but particularly the reactor, have to be extremely light, so that the wall thickness of the latter has to be kept to a srict minimum.

These principles however do no match with other requirements especially those concening ballistic accuracy. Rocket thrust and burning duration, to mention but the most important parameters in the art, are directly proportional to the pressure set up during combustion within the reactor. This pressure, however, being dependcut on volume and temperature conditions, must be kept rather low, if hazards of damaging if not bursting the reactor, the strength of which having already decreased under the impact of the high temperatures involved, shall be precluded.

In order to overcome these difliculties and to reconcile the different tactical, ballistic and safety requirements, it has been proposed to line the reactor with a protective layer acting as a thermal insulator. Also, it has been proposed to incorporate a safety valve in the reactor, in such a manner that this valve, being positioned at the rear of the reactor like a nozzle, opens automatically when a critical pressure is attained. While such thermal insulation does not take into consideration hazardous overpressures, application of a safety valve may affect seriously the ballistic accuracy of the projectile, which undergoes an additional and unforeseen power impulse when the valve opens.

My invention aims at obviating the aforedescribed disadvantages and contemplates a very simple device comprising substantially a safety piston, which is movable along the axis of the projectile and which can be incorporated in any powder rocket reactor.

According to my invention, the aforesaid piston is adapted to be displaced when a predetermined gas pressure has been reached, thus increasing the volume of the combustion chamber in such a manner that the pressure, without exceeding a critical limit, keeps constant throughout the burning duration.

In order to enable my invention to be more readily understood, reference is made to the following description and to the accompanying drawings, which illustrate, by way of example, a preferred embodiment thereof, and in which:

Fig. 1 shows in a sectional longitudinal view a powder reactor comprising the safety pistonin accordance with the invention.

Fig. 2 is a fragmentary sectional longitudinal view of the brim of the safety piston shown in Fig. I.

As shown in Fig. 1, the rocket reactor 1 is of conventional design and includes a reaction chamber with United States Patent 0 nozzle 2 for the combustion of a self-propellent powder charge 3 to be ignited by a suitable pyrotechnic primer 4. The combustion chamber is partitioned by a safety piston 5, secured thereto in a suitable manner such as by shoulder 6 which is either inserted into a recess of the reactor wall or in abutting engagement with the rearward end of a sleeve 7. In the following description reference is made to a combustion chamber comprising a sleeve, though the first mentioned means of securing the piston to the combustion chamber are equally possible without departing from the spirit and scope of the invention as claimed.

Disposed within sleeve 7 is safety piston 5, with a generally, cylindrical body having an exterior diameter such as to allow for almost no play between sleeve and piston. An axial bore may be formed within piston 5 Between the outer face of piston 5 and the forward end 8 of the combustion chamber there is a recess into which the piston can slide when the resistance set up by frictional forces and by shoulder6 is neutralized as by overpressures. Provided there is sufficient space Within the piston body and in case the self-propellent powder charge 3 is ignited from its forward end, pyrotechnic primer 4 is, preferably, mounted within the piston. Such design confers the further advantage that safety piston 5 will be dilated radially by the defiagration of the primer mixture, sealing tightly the forward end of the combustion chamber at the very start of the combustion.

The brim 9 at the open end of'piston 5, as shown with shoulder 6 in a fragmentary view in Fig. 2, is shaped and dimensioned in such a manner that whenever an axial stress is exerted upon shoulder 6, this stress, which can be logically developed in the'direction from nozzle to piston only will become effective as a pure shearing stress in the critical section of shoulder 6 indicated by dotted lines in Fig. 2. To prevent the shoulder from being distorted by flexiorl, brim 9 must have a minimum height dependent on the forces'involved, this height being measured from the shoulder to the rearward end of the piston.

The thickness of shoulder 6 depends on the stress at which it has to yield and break away. Since overpressures impinging upon the inner face of safety piston 5, cause shearing stresses only upon shoulder 6, this latter is then almost instantaneously torn off from the piston ody.

The operation of the safety piston device according to my invetnion will be clear from the foregoing description.

As long as the gas pressure in the reactor keeps at its normal value, thus insuring ballistic accuracy of the projectile and an adequate safety factor for the reactor walls, safety piston 5 is retained in its initial position, such normal pressure being inferior to the resistance set up by shoulder 6 and by the piston body which is jammed radially, by the same pressure, into sleeve 7. The combustion chamber is such confined by planes A-A and B-B of Figure 1.

When the pressure, however, exceeds the predetermined magnitude, risking damage to the reactor, shoulder 6 is sheared off and piston 5, against frictional resistance, is urged into the recess at the forward end of the reactor, this movement coming to a standstill either whenbe made in size, shape, and arrangement without departing from the spirit and scope-of the invention as claimed.

I claim: t

l. A powder reactor for self-propelled projectiles comprising a combustion chamber having arecess therein, a safety pistonpartitioning saidchamber and a powder self-,propel lent charge disposed within said chamber be- :tween a nozzle of said reactor andthe rear-end of said piston, said piston'having a shoulderand being frangibly secured to the wallof said combustion chamberrby means of the shoulder with the latter inserted into the recess in the wall so that when such overpressures occur the shoulder will shear-to allow the piston-to move, whereby overpressur'es of gases generated by the combustion of saidrself-propellent charge and exceeding a predetermined ,rnagnitude kaxiall y displace said piston and increase the combustion volume to thereby reduce saidoverpressures.

2. A powder reactor for self-propelled projectiles comprising a combustion chamber having a recess therein, a safety piston partitioning said chamber and a powder self-propellent charge disposed within said chamber between a nozzle of said reactor and the rear end of said piston, said piston having a shoulder and being frangibly secured to the wall of said combustion chamber by means of the shoulder with the latter inserted into the recess in the wall, sothat when such overpressures occur the shoulder will shear to allow the piston to move, and a sleeve disposed within said chamber, saidshoulder being in abutting engagement with the rearward end of the sleeve whereby the body of said piston is disposed and guided within said sleeve, whereby overpres'sures of gases generated by the combustion of said self-propellent charge and exceeding a predetermined magnitude axialiy displace said piston and increase the combustion volume to thereby reduce said overpressures.

3. A powder reactorfor self-propelled projectilescomprising a combustion chamber having a recess therein, a safety piston partitioning said chamber and a powder self-propellent chargeldisposed within said chamber between a nozzle of said reactor and the rear end of said piston, the play between said piston and its chamber being such, that upon firing of a primer disposed within said piston, and upon the start of combustion of said self-propellent charge, said' piston is jammed into its chamber and is capable of moving from its jammed position to a new position, whereby overpressures of gases generated by the combustion of said self-propellent charge and exceeding a predetermined magnitude axially displace said piston and increase the combustion volume to thereby reduce said overpressures.

4. A powder reactor for self-propelled projectiles comprising a combustion chamber having a recess therein, a safety piston partitioning said chamber and a powder self-propellentcharge disposed Within said chamber between a nozzlerof saidreactorand the rear end of said piston, said pistonrhaving a shoulder and being secured to the wall of said combustion chamber by means of the shoulder with the latter inserted into the recess in the wall, a brim of said piston having a height measured from said shoulder so that the stresses directed against the inner face of said piston and exerted axially upon said shoulder, become effective exclusively as shearing stresses in the critical section of said shoulder, whereby overpressures of gases generated by the combustion of said self-propellent charge and exceeding a predetermined magnitude axially displace said piston and increase the combustion volume to thereby reduce said overpressures.

5. A powder reactor for self-propelled projectiles comprising a combustion chamber having a recess therein, a safety piston partitioning said chamber and a powder selfpropellent charge disposed within said chamber between a nozzle of said reactor and the rear end ofsaid piston, the recess being provided between the outer face of said piston and the forward end of said combustion chamber,

said piston having a retaining means, and said piston being urged into said recess by overpressures of the combustion gases neutralizing the resistance of the retaining means of said piston, whereby overpressures of gases generated by the combustion of said self-propellent charge and exceeding a predetermined magnitudeaxially displace said piston and increase the combustion volume to thereby reduce said overpressures.

References Cited in the file of this patent UNITED STATES PATENTS 

